Changes in arterial wall properties during development and maintenance of renal hypertension.

Segments of carotid and tail arteries were used to determine the effects of two-kidney Goldblatt hypertension on mechanical properties and chemical contents. Arteries were obtained after 4 and 12 wk of hypertension. Systolic pressures averaged 129 mmHg in control animals and 150 mmHg in hypertensive ones. Pressure-diameter data were recorded under conditions of active (145 mM K+) and passive (0 Ca2+ and 2 mM EGTA) smooth muscle. Small increases in passive stiffness were found after 4 and 12 wk in the carotid arteries of hypertensive animals, but no significant change occurred in the tail arteries. Small but significant decreases in total connective tissue content of these arteries were found after 12 wk of hypertension. Maximum values of active stress response were significantly larger in carotid arteries from hypertensive animals at both 4 and 12 wk of hypertension. No significant differences were found for the tail arteries. The K+ content of the carotid but not the tail artery was larger for the hypertensive animals. When corrected for differences in relative cell content most of the differences in active force development were eliminated. The differences in passive mechanics can not be explained on the basis of the changes in connective tissue content. The active smooth muscle responses and content changes suggest that they are directly related to the moderate elevation of arterial pressure.